The present invention relates to a sliding member for a compressor.
In a piston type compressor having a hemispherical shoe as a sliding member disposed between a piston and the sliding surface of a swath plate, the shoe has on the surface thereof a coating layer having relatively good sliding to property for preventing wear of the sliding surfaces between the swash plate and the shoe, and also between the piston and the shoe.
The use of a diamond-like carbon (amorphous hard carbon film) as a coating layer on the shoe surface is disclosed, for example, in Japanese Patent Publication Application No. 6-346074. The diamond-like carbon layer is a hard carbon film having excellent sliding property under severe lubrication condition.
However, in a case where an aluminum alloy having relatively low hardness is used for a base metal of the shoe and the diamond-like carbon layer is formed directly on the surface of the shoe, the diamond-like carbon layer tends to be separated or peeled off from the base metal due to a large difference in hardness between the base metal and the diamond-like carbon layer.
Japanese Patent Application Publication No. 2002-194565 discloses a shoe having on the surface of the base metal thereof a nickel-phosphorus plating layer as a nickel-based plating layer and a diamond-like carbon layer formed on the surface of the nickel-phosphorus plating layer. The difference in hardness between the nickel-phosphorus plating layer and the diamond-like carbon layer is smaller than that between the base metal and the diamond-like carbon layer, which makes possible to prevent the diamond-like carbon layer being separated or peeled off from the base metal of the shoe when the diamond-like carbon layer having relatively high hardness is formed on the base metal made of an aluminum-based metal.
In the case where the diamond-like carbon layer is provided directly on the nickel-phosphorus plating layer, however, there is a problem in that adhesion of the diamond-like carbon layer to the nickel-phosphorus plating layer is low.
Therefore, the present invention is directed to a sliding member for a compressor which can improve the adhesion between the nickel-based plating layer and the diamond-like carbon layer.